1. Field of the Invention
The present invention relates to an image display apparatus and method, and in particular, to an image display apparatus and method for converting a viewpoint of an original image of the driving environment obtained with an imaging device to display a bird's eye view image.
2. Description of the Related Art
There is conventionally known a parking assisting device mounted on a vehicle to allow an operator to recognize a distance to an obstruction and so forth Such a device obtains an original image by imaging the driving environment with a camera mounted on the vehicle, and converts the viewpoint of the obtained image based on a depression angle of the camera, to generate and display a bird's eye view image to the operator. When the vehicle is operated on an actual road, however, the angle of the camera relative to the road surface changes according to various factors such as bumps and dips and inclination of the road surface, cargoes carried by the vehicle, and deterioration of the vehicle over years, which makes it impossible to obtain a correct bird's eye view image by viewpoint conversion using the initially set depression angle of the camera. Such changes in angle of the camera relative to the road surface may result in bird's eye view images at a different scale or with unnatural distortion.
In order to solve this problem, Japanese Patent Application Publication No. 2003-274394 (JP-A-2003-274394) discloses a related art that uses a laser emission device for emitting a directional laser beam and a height sensor to measure an angle of a camera relative to a road surface, and that adds a correction angle to a depression angle of the camera based on the measurement results to generate a bird's eye view image in accordance with changes in angle of the camera relative to the road surface.
The above related art, however, is built on the premise that there is no three-dimensional object present on the road surface. Therefore, a three-dimensional object on the road surface such as curbs and car stoppers, if any, is regarded as a part of the road surface in calculating a correction angle for the depression angle of the camera, even though such a three-dimensional object does not in fact affect the angle of the camera relative to the road surface. Thus, an unexpected correction angle is obtained, which consequently results in display of a bird's eye view image that is significantly uncomfortable to the operator.